1. Field of the Invention
The present invention relates generally to the installation of a wiring harness used for interconnecting electrical equipment and/or circuits and, more particularly, to a method and apparatus for dressing or enshrouding such a wiring harness for installation of the harness through an opening of a structural member during manufacture of a product including the structural member. The present invention is particularly applicable to the manufacture of motor vehicles and accordingly will be described with reference to that application.
2. Description of the Related Art
Wiring harnesses used for motor vehicle electrical circuits are normally preformed as a central bundle of electrical conductors. Projecting from the bundle at varying locations along its length are pigtails, takeouts, connectors, harness hold-downs and the like which may be referred to herein as extensions. The extensions serve to make connections from electrical circuits or equipment to or through the electrical conductors of the wiring harness to associated electrical circuits or equipment or to hold the harness in place in the motor vehicle. Oftentimes, preformed wiring harnesses must be routed through openings in structural members, for example through the firewall of a motor vehicle, to make the required connections. When a wiring harness is to be passed through an opening, the extensions tend to catch on the opening and interfere with quick and easy installation of the harness.
Prior to this time, extensions from a wiring harness typically have been taped against the central bundle or trunk of the wiring harness to facilitate installation. Unfortunately, the application of tape to the individual extensions is a time consuming operation.
An alternate wiring harness dressing arrangement involves the use of tubular "heat shrink" material. The extensions from the wiring harness are held against the harness trunk and a length of tubular heat shrink material is slid over the harness. Heat is then applied to the heat shrink material causing it to shrink or reduce in size and trap the extensions down to substantially the size of the wiring harness trunk. The dressed wiring harness is then inserted through an opening in a motor vehicle firewall or other structural element. Once fully inserted, the shrink wrap material is ripped from the wiring harness to release the extensions for the remainder of the installation of the wiring harness.
However, the application of heat shrink material to wiring harnesses requires substantial floor space, the application process is difficult to control, the application requires at least as much labor as taping and the heat shrink material is more expensive than tape. Further, there have been problems in removing the heat shrink material. Perforations have been formed in the heat shrink material to attempt to overcome the removal problem. However, even if perforations are provided, problems may persist since excessive heat can bond the perforated sections together. Of course, there is also the possibility that excessive heat will damage the wiring harnesses.
A further method is disclosed in U.S. Pat. Nos. 5,064,970, and 5,293,501, each assigned to the assignee of the instant invention by Bennett et al. Bennett teaches the use of a tubular section or sock of stretchable material comprises a generally rectangular piece of cloth having two opposed short sides and two opposed long sides. The long sides of the piece of cloth are joined to one another by a single thread chain stitch and tab means for securing the chain stitch at one end of the tubular means. The wiring harness is then contained within the sock and routed through openings in the structural members. Thereafter the tab means is forcibly removed from the shroud to open the tubular section of stretchable material by freeing or releasing the chain stitch.
Unfortunately, once the chain stich is removed the cloth must be disposed or reprocessed. Disposing each sock after one use is expensive and increases solid waste output of the manufacturing plant. Reprocessing the sock requires the prohibitively expensive off-site replacement of the chain stich.
In a related field, it is known to use a wraparound closure device having a symmetrical zipper to protect elongate substrates from abrasion. One such method is disclosed U.S. Pat. No. 4,891,256, Kite. Kite teaches a device that bundles cables while allowing future access for repair. More specifically the device is particularly intended for use with cables that are already installed. While this is acceptable in the stationary application, it is not suitable for the pass through application intended by the instant invention.
Kite requires that the slide be manually actuated along the entire length of the zipper. Once the wraparound closure is installed over a bundle of cables, Kite does not teach how to easily remove the wraparound closure when the cables are installed through structual elements and are located in a confined area. This is especially difficult due to the tendency of the enshrouded wiring harness to bunch and twist upon installation. It is thus almost impossible to manipulate a slide over an undulating and twisting surface to unzip the shroud. The unzipping is further complicated by the great possibility of the slide snagging on the wiring harness connections. It is therefore extremely difficult for Kite III to be utilized for the dressing and installation of wiring harnesses.
Accordingly, there is a need for an improved method and apparatus for dressing wiring harnesses for installation through openings in firewalls or other structural elements of motor vehicles and other products. Preferably the improved wiring harness installation method and apparatus would utilize inexpensive materials, and be readily applied to and quickly and easily removed from the wiring harness. Further, the preferred apparatus would permit recycling or reuse to greatly reduce the expenses involved in wiring harness iinstallation operations